In the case of a fracture of the ankle bone as well as in certain cases of ankle sprain or strain, it is generally necessary to secure the ankle against motion in a cast during an appropriate length of time, in order to allow the fractured parts of the bone to knit together and the ligaments to heal.
When this cast is removed, it is often impossible for the patient to rotate the foot, on account of the ankylosis or stiffening caused by the lapse of time of immobility.
To recover the mobility of the foot, it is necessary then to initiate a rehabilitation of the normal motions and this rehabilitation is often left to the patient alone to carry out appropriate exercises of the ankle.
When the patient carries out such exercises in a standing position, the portion of the weight of the body on the injured foot may cause bruising and pain which makes rehabilitation difficult.
When the patient carries out such motions in a sitting or lying position, the suspended position of the leg rapidly produces considerable pain.